1. Field of the Invention
A method of synchronizing wireless communication between a first electronic device and a second electronic device utilizing frequency hopping spread spectrum communication systems.
2. Description of the Prior Art
Frequency hopping spread spectrum communication systems frequently include a first electronic device, such as a computer, having a transmitter and a second electronic device, such as a PDA, laptop, or printer, having a receiver. The first electronic device partitions data into a plurality of data blocks and spreads the transmission of the data blocks over a plurality of frequency channels. Each of the plurality of data blocks is modulated into a distinct and separate signal. The transmitter transmits the signal at the radio frequency channel for a predetermined time, or dwell time. A portion of the dwell time contains frequency hop information about the next frequency channel to which the transmitter will be transmitting on. The transmitter selects the radio frequency channels in a predetermined pseudo-random pattern. By transmitting the data in blocks and at random radio frequency channels, there is little chance that any unintended recipients will intercept the data, therefore creating a secure transmission. Other transmitters described in the prior art do not incorporate frequency hopping information as part of the signal, but requires the receiver to learn the hopping pattern by tracking the hops of the transmission and synchronizing during each hop. Both devices must devices must then spend a undetermined amount of time to synchronize.
The prior art receivers monitor the plurality of radio frequency channels for the transmittance of any signals being transmitted on those channels. The receiver detects the signal and demodulates the data block and receives the hopping information. The receiver then selects the next radio frequency channel to monitor for a signal. However, these receivers do not know when the transmitter is going to transmit the signal or at which of the plurality of radio frequency channels the transmitter will transmit on. Hence, the receivers are required to maintain a powered-on state for detection of the signal. Additionally, the synchronization of the receiver is very slow when it monitors the entire range of frequency channels.
Accordingly, it would be advantageous to provide a system wherein the transmitter and the receiver were able to synchronize rapidly thereby decreasing the synchronization time and without compromising the security of the transmission.
The subject invention provides a method of synchronizing wireless communication between a first electronic device having a transmitter and a second electronic device having an amplitude modulated (AM) receiver and at least one frequency modulated (FM) receiver which communicates via frequency hopping spread spectrum signals. The first step of the method is partitioning data stored within the first electronic device into a plurality of data blocks for transmittance of the data blocks over wireless connections to the second electronic device. Then the data blocks are spread over a plurality of frequency channels such that each of the data blocks is transmitted on a different frequency channel for creating a secure transmission link between the first electronic device and the second electronic device. The data block is modulated at a radio frequency channel to establish a signal having amplitude modulated (AM) characteristics and the signal is transmitted at the radio frequency channel to establish a connection between the first electronic device and the second electronic device. The method further includes the step of detecting the AM characteristics of the signal with the AM receiver and measuring a time period beginning at the detection of the signal by the AM receiver and ending when the signal is no longer detected for decreasing the synchronization time between the first electronic device and the second electronic device. The method is characterized by scanning the plurality of frequency channels with a frequency modulated (FM) receiver during the measured time period such that the second electronic device knows when the first electronic device is transmitting the signal.
The method allows for the FM receiver to more rapidly synchronize with the transmitter which allows for faster data transmission. In our work environments, many devices will be communicating via radio frequencies and the need for rapid transmission of data to free up other frequency channels will be extremely important for wireless communication to be effective. Additionally, only the AM receiver must remain in a powered-on state while scanning the frequency channels which reduces the power consumption.